Garage consumer unit

[ricosuave]

Hi all, have just fitted garage consumer unit it has RCD, 32A breaker for ring and 6A breaker for lights can i use 2.5 cable from house consumer unit to supply garage consumer unit?
House c/u is about 3 meters from garage c/u and also would house circuit breaker have to be 32A or 40A?

I am new to forums and dont know where this will be posted or how to get a reply so can you email me the answer to my question and how to use these forums many thanks, [email protected]
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[ezzzekiel]

Can you provide us with your level of competence, qualifications and experience then maybe we can help a bit more, cause as it stands you seeem as though you have no understanding at all on a very basic level.

 

[Inward123]

I think the problem is what the guy has asked is actually a very common set up and one that I find all the time in most houses. I'm not an electrician an always go with what one says but it would help if someone could explain why it so basd even if not the anser then the downsides - particularly as I find this a very common installation in my job of installing interiors and kitchens.

 

[Adam W]

NovusSparkus, What would you recommend to supply this then?

It's not quite as simple as that - you need to select a cable type appropriate to the conditions, take rating factors into consideration (eg thermal insulation) and from the tables in the back of the regs book select a size suitable for the demand of the submain, which you will have calculated.

 

[nickblake]

Im backing up pushrods post here , a reason you cant do it , if you are installing a consumer unit in the garage with circuits comming off then there is a possibility that there could be an over load of the 2.5mm cable supplying the garage , power tool heaters lights , lawn mowers naming just a few ,appendix 15 of BS7671 does state you can use a spur from a ring to supply a socket , or fused spur / socket combination , if he said that he wanted to put a single socket in his garage and a light via a fused spur off a radial from a socket in the house then there would not have been a problem ,as the house is joined to the garage,but the way realy to do it is to get a Part P regestered spark to install a sub main from the main consumer unit to the garage consumer unit , in a suitable rated cable, also as been pointed out the work is notifiable by law

 

[Des 56]

Inward123 the common set up as you describe it cant exist as a pick it off the shelf one size fits all,for the very reasons given by NovusSparkus

Distribution cable sizes need to have calculations made of the various factors and the intended load, before deciding on the type and size of overcurrent and earth fault protection,also consideration of the supply earthing arrangements in relation to the services that may or may not be in the garage

 

[Inward123]

Just saying the majority of houses that I see are typically 2-5 bed with garage and always look to have the following a separate consumer unit (supplied by 2.5mm cable) In the garage the unit sometimes are fitted with a 63 a rcd and typically with a 2.5mm rated cable to between 2-4 sockets and the lighting circuit is typically a single batten florescent to a 6 am mcb

 

[Qedelec]

Just saying the majority of houses that I see are typically 2-5 bed with garage and always look to have the following a separate consumer unit (supplied by 2.5mm cable) In the garage the unit sometimes are fitted with a 63 a rcd and typically with a 2.5mm rated cable to between 2-4 sockets and the lighting circuit is typically a single batten florescent to a 6 am mcb

The number of beds does not come into the equation. The point is what can be connected to the final circuit.
From his previous posts he appears to be considering coming off the ring main which is most likely fused at 32amps.
Consider what will happen if someone in the future decides to use a welder in the garage, (a very possible senario), and thinks that because the supply is installed to regs that he can draw the maximum current allowed by the MCB's.

 

[nickblake]

Just saying the majority of houses that I see are typically 2-5 bed with garage and always look to have the following a separate consumer unit (supplied by 2.5mm cable) In the garage the unit sometimes are fitted with a 63 a rcd and typically with a 2.5mm rated cable to between 2-4 sockets and the lighting circuit is typically a single batten florescent to a 6 am mcb

The RCD is not an over load device the rating of the RCD is the current capacity of the contacts,it could be 100 amps or 10 amps makes no difference to over load , if it was a fused spur then its a differant matter

 

[Inward123]

Thanks guys for the clarification just out of interest here is my situation (installed by a qualified electrician) I have a garage with the following 4 double sockets terminating on to a 16a mcb (spur not ring) and a double batten florescent fitting on a 6 mcb (40 a rcd is part of the same unit) this terminates through and adjoining wall in a run of no more than a meter on to a modern consumer unit using its own 32a mcb (ie the garage has it's own circuit/mcb) - the biggest thing it Powers in my garage is either my pressure washer or washing machine not used at the same time because of the water pressure. Should I worry ?

 

[Qedelec]

From what you say the max draw would be 22amps (16 + 6) so 32amp supply should be fine. what earth arrangements have been provided?

 

[nickblake]

from the main consumer unit the cable should be a minimum of 4mm but would be better with 6 mm , if its 2.5mm cable then the maximum MCB size should be 20 amp

 

[Inward123]

Think I can sleep easily here sorry for MCB is 20 amp (my mistake) earth looks to be a on to both a cold water pipe and a rod/piece of rebar thanks guys

 

[nickblake]

No problem